Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$205.28	9.387%	$224.5496	$224.55	$224.55	$224.50
Purchase #2	$196.47	13.578%	$223.1467	$223.15	$223.15	$223.10
Purchase #3	$223.26	8.580%	$242.4157	$242.42	$242.40	$242.40
Purchase #4	$103.59	13.145%	$117.2069	$117.21	$117.20	$117.20
Purchase #5	$174.61	12.638%	$196.6772	$196.68	$196.70	$196.70
Purchase #6	$21.57	11.312%	$24.01	$24.01	$24.00	$24.00
Purchase #7	$35.37	5.841%	$37.436	$37.44	$37.45	$37.40
7 purchase totals =	$960.15		$1,065.4421	$1,065.46	$1,065.45	$1,065.30